U.S. patent number 7,395,617 [Application Number 11/012,867] was granted by the patent office on 2008-07-08 for air passage device for inflatable shoe bladders.
This patent grant is currently assigned to Reebok International Ltd.. Invention is credited to Brian Christensen, Paul M. Davis.
United States Patent |
7,395,617 |
Christensen , et
al. |
July 8, 2008 |
Air passage device for inflatable shoe bladders
Abstract
An inflatable bladder for use in an article of footwear
including a first sheet of a flexible fluid-impervious material and
a second sheet of flexible fluid-impervious material. The first
sheet and the second sheet are sealed along air-tight weld lines
forming at least one narrow channel. The inflatable bladder
includes an air passage device for maintaining air flow within the
narrow channel. In one embodiment, the first sheet has an embossed
interior surface to limit the contact between the first sheet and
second sheet. Another embodiment includes the use of a mechanical
device to separate the first sheet and the second sheet within a
narrow channel. A method of manufacturing an inflatable bladder, a
method of increasing localized air flow though a narrow channel of
an inflatable bladder for use in an article of footwear and an
article of footwear incorporating the inflatable bladder are also
described.
Inventors: |
Christensen; Brian
(Centerville, MA), Davis; Paul M. (Blackstone, MA) |
Assignee: |
Reebok International Ltd.
(Canton, MA)
|
Family
ID: |
36593921 |
Appl.
No.: |
11/012,867 |
Filed: |
December 16, 2004 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20060130369 A1 |
Jun 22, 2006 |
|
Current U.S.
Class: |
36/45; 156/292;
156/308.4; 36/29; 36/88 |
Current CPC
Class: |
B29D
35/122 (20130101); A43B 13/20 (20130101) |
Current International
Class: |
A43B
7/14 (20060101) |
Field of
Search: |
;36/29,88,45,93
;156/145,242,292,308.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Stevens Urethane Film & Sheet: The high-performance material
for today's `can't fail` applications," Stevens Urethane, Holyoke,
MA (date unknown). cited by other .
Printout of Stevens Urethane website at
www.stevensurethane.com/filmsheet/filmsheet.sub.--aromatic.html
entitled "Aromatic Sheet," (date unknown). cited by other .
Stevens Urethane "ST-1880 Polyether, Polyurethane" information
Sheet, (date unknown). cited by other .
Printout of Stevens Urethane website at
www.stevensurethane.com/urethanepeople/callout.sub.--atheleticshoe.gif
entitled "Athletic Shoes," (date unknown). cited by other.
|
Primary Examiner: Patterson; Marie
Attorney, Agent or Firm: Sterne, Kessler, Goldstein &
Fox P.L.L.C.
Claims
What is claimed is:
1. An article of footwear comprising: an upper; a sole attached to
said upper; and an inflatable bladder introduced into at least one
of said upper and said sole; wherein said inflatable bladder
includes a first sheet of a fluid-impervious material having an
interior surface and a second sheet of fluid-impervious material
having an interior surface, wherein said first sheet and said
second sheet are sealed wherein at least a portion of the interior
surface of said first sheet is in contact with at least a portion
of the interior surface of said second sheet, and wherein
substantially all of said first sheet has an embossed interior
surface that limits said interior surface contact between said
first and second sheets.
2. The article of footwear of claim 1, wherein a portion of said
second sheet has an embossed interior surface.
3. The article of footwear of claim 1, wherein at least said first
sheet includes a layer of thermoplastic film.
4. The article of footwear of claim 3 wherein at least said first
sheet is a laminate of a thermoplastic film and substrate.
5. The article of footwear of claim 4, wherein said substrate is a
textile.
6. The article of footwear of claim 5, wherein said substrate is a
non-woven nylon and polyethylene blend.
7. The article of footwear of claim 3, wherein said thermoplastic
film is selected from the group consisting of polyurethanes,
ethylenevinylacetate/polyethylene copolymer; polyester elastomer;
ethylenevinylacetate/polypropylene copolymer; polyethylene;
polypropylene; neoprene; natural rubber; dacron/polyester;
polyvinylchloride; thermoplastic rubbers; nitrile rubber; butyl
rubber; sulfide rubber; polyvinyl acetate; methyl rubber; buna N.;
buna S.; polystyrene; ethylene propylene; polybutadiene;
polypropylene; silicone rubber, chlorsulfonated polyethylene and
nylon.
8. The article of footwear of claim 7, wherein said thermoplastic
film is selected from a group consisting of a polyester urethane
film and a polyether urethane film.
9. An inflatable bladder for use in an article of footwear,
comprising: a first sheet of a fluid-impervious material having an
interior surface and a second sheet of fluid-impervious material
having an interior surface, wherein at least a portion of an
interior surface of said first sheet is in contact with at least a
portion of the interior surface of said second sheet, wherein said
first sheet and said second sheet are sealed and substantially all
of said first sheet has an embossed interior surface that limits
said interior surface contact between said first and second
sheets.
10. The inflatable bladder of claim 9, wherein at least a portion
of said second sheet has an embossed interior surface.
11. The inflatable bladder of claim 9, wherein each of said first
and second sheets includes a layer of thermoplastic film.
12. The inflatable bladder of claim 11 wherein at least one of said
first sheet and said second sheet is a laminate of a thermoplastic
film and substrate.
13. The inflatable bladder of claim 12, wherein said substrate is
made from a textile.
14. The inflatable bladder of claim 13, wherein said substrate is a
non-woven nylon and polyethylene blend.
15. The inflatable bladder of claim 11, wherein said thermoplastic
film is selected from the group consisting of polyurethanes,
ethylenevinylacetate/polyethylene copolymer; polyester elastomer;
ethylenevinylacetate/polypropylene copolymer; polyethylene;
polypropylene; neoprene; natural rubber; dacron/polyester;
polyvinylchloride; thermoplastic rubbers; nitrile rubber; butyl
rubber; sulfide rubber; polyvinyl acetate; methyl rubber; buna N.;
buna S.; polystyrene; ethylene propylene; polybutadiene;
polypropylene; silicone rubber, chlorsulfonated polyethylene and
nylon.
16. The inflatable bladder of claim 15, wherein said thermoplastic
film is selected from a group consisting of a polyester urethane
film and a polyether urethane film.
17. A method of manufacturing an inflatable bladder for an article
of footwear, comprising: providing a first fluid-impervious sheet
having an interior surface and a second fluid-impervious sheet
having an interior surface, wherein at least a portion of the
interior surface of said first sheet is in contact with at least a
portion of the interior surface of said second sheet, wherein
substantially all of said first sheet includes a first embossed
interior surface that limits said interior surface contact between
said first and second sheets; positioning said first embossed
surface interior surface adjacent to and facing a second interior
surface of said second sheet; and sealing said first and second
sheets together to form an inflatable bladder.
18. The method of claim 17, wherein at least a portion of said
second interior surface is an embossed surface.
19. The method of claim 17, wherein each of said first and second
sheets includes a layer of a thermoplastic film.
20. The method of claim 19 wherein at least one of said first sheet
and said second sheet is a laminate of a thermoplastic film and
substrate.
21. The method of claim 20, wherein said substrate is made from a
textile.
22. The method of claim 21, wherein said substrate is a non-woven
nylon and polyethylene blend.
23. The method of claim 19, wherein said thermoplastic film is
selected from the group consisting of polyurethanes,
ethylenevinylacetate/polyethylene copolymer; polyester elastomer;
ethylenevinylacetate/polypropylene copolymer; polyethylene;
polypropylene; neoprene; natural rubber; dacron/polyester;
polyvinylchloride; thermoplastic rubbers; nitrile rubber; butyl
rubber; sulfide rubber; polyvinyl acetate; methyl rubber; buna N.;
buna S.; polystyrene; ethylene propylene; polybutadiene;
polypropylene; silicone rubber, chlorsulfonated polyethylene and
nylon.
24. The method of claim 23, wherein said thermoplastic film is
selected from a group consisting of a polyester urethane film and a
polyether urethane film.
25. An inflatable bladder for use in an article of footwear
comprising: a first sheet of a fluid-impervious material having an
interior surface; a second sheet of a fluid-impervious material
having an interior surface, wherein at least a portion of the
interior surface of said first sheet is in contact with at least a
portion of the interior surface of said second sheet, wherein said
first sheet and said second sheet are sealed; and at least one
narrow channel between said first and second sheets, wherein at
least a portion of an interior surface of said first sheet along
said narrow channel is embossed to limit said interior surface
contact between said first and second sheets, wherein a substrate
is laminated to a portion of an interior surface of at least said
first sheet, and wherein said first sheet includes an embossed
thermoplastic film, and wherein said first sheet is a laminate of a
thermoplastic film and substrate.
26. A method of increasing localized air flow through a narrow
channel of an inflatable bladder for use in an article of footwear,
comprising: providing a first fluid-impervious sheet having an
interior surface and a second fluid-impervious sheet having an
interior surface, wherein at least a portion of the interior
surface of said first sheet is in contact with at least a portion
of the interior surface of said second sheet; embossing at least a
portion of an interior surface of one of said first or second
sheets to limit said interior surface contact between said first
and second sheets; sealing said first sheet and said second sheet
to form an inflatable bladder having at least one narrow channel,
wherein said embossed material is a substrate laminated to a
portion of an interior surface of at least said first sheet.
Description
FIELD OF THE INVENTION
The present invention relates generally to the use an air passage
device in the manufacture of inflatable bladders for use in
athletic footwear and to athletic footwear including such a
bladder.
BACKGROUND OF THE INVENTION
Inflatable bladders have been used in articles of footwear as
cushioning within shoe soles and shoe uppers. When positioned
within a shoe upper, an inflatable bladder may be used to provide
cushioning as well as improve the fit of the article of footwear.
In some cases, the bladder may be used instead of conventional
lacing to hold the shoe on the foot of the user. Inflatable
bladders may also be used under the foot of the wearer to cushion
the impact of the foot as it moves through a gait cycle.
Inflatable bladders may be, for example, formed from two sheets of
fluid-impervious thermoplastic film that have been sealed together
to form an air-tight chamber. For example, U.S. Pat. No. 6,785,985
and U.S. patent application Ser. No. 10/887,927, which are
incorporated by reference herein in its entirety, disclose bladders
formed from sheets of a light urethane film, a polyester film such
as MYLAR.RTM., an ethyl vinyl acetate film or another barrier film.
For example, bladders for footwear have been made from a matted
polyurethane film commercially available from J. P. Stevens &
Co (Easthampton, Mass.) under the product number ST-1880 M2. Two
sheets of thermoplastic film are sealed along various weld lines,
for example by radio frequency (RF) welding, to form an air-tight
inflatable bladder.
However, where weld lines are close together and form a narrow
fluid channel within the bladder, air movement through the narrow
channels may become restricted causing squeaking with each step
taken by the wearer due to tight flow tolerances. Also, the
interior surfaces of the bladder may have a tendency to temporarily
adhere or stick together, due to static, friction or the nature of
the materials.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the present invention is an inflatable bladder
for use in an article of footwear including a first sheet of a
flexible fluid-impervious material and a second sheet of flexible
fluid-impervious material. The first sheet and the second sheet are
sealed along air-tight weld lines forming at least one narrow
channel. The inflatable bladder includes an air passage device for
maintaining air flow within the narrow channel. The air passage
device limits the surface contact between the first and second
sheets and avoids noises caused by restricted air movement along
narrow channels.
Another embodiment of the present invention is an article of
footwear including an upper, a sole attached to the upper, and an
inflatable bladder introduced into at least one of the upper and
the sole. The inflatable bladder includes a first sheet of a
flexible, fluid-impervious material and a second sheet of flexible,
fluid-impervious material. The first sheet and the second sheet are
sealed along an air-tight peripheral weld line, and at least the
first sheet has an embossed interior surface.
Another embodiment of the present invention is an inflatable
bladder for use in an article of footwear including a first sheet
of a flexible, fluid-impervious material and a second sheet of
flexible, fluid-impervious material. The first sheet and the second
sheet are sealed along an air-tight peripheral weld line. At least
the first sheet has an embossed interior surface.
Another embodiment of the present invention is a method of
increasing localized air flow through a narrow channel of an
inflatable bladder for use in an article of footwear. The method
includes providing a first flexible, fluid-impervious sheet and a
second flexible, fluid-impervious sheet. The first sheet and the
second sheet are sealed along air-tight weld lines to form an
inflatable bladder having at least one narrow channel. An air
passage device is provided at least within the narrow channel.
Another embodiment of the present invention is a method of
manufacturing an inflatable bladder for an article of footwear. The
method includes providing a first flexible, fluid-impervious sheet
and a second flexible, fluid-impervious sheet. The first sheet
includes a first embossed interior surface. The first embossed
interior surface is positioned adjacent to and facing a second
interior surface of the second sheet. The first and second sheets
are sealed together along a desired peripheral weld line to form an
air-tight bladder. The first and second sheets are cut out along an
exterior edge of the peripheral weld line.
Further embodiments, features, and advantages of the present
invention, as well as the structure and operation of the various
embodiments of the present invention, are described in detail below
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
The accompanying drawings, which are incorporated herein and form a
part of the specification, illustrate the present invention and,
together with the description, further serve to explain the
principles of the invention and to enable a person skilled in the
pertinent art to make and use the invention.
FIG. 1 is depiction of the manufacturing process used to form a
bladder of an article of footwear of the present invention.
FIG. 2 is a plan view of an embossed film for use in the present
invention.
FIG. 3 is a sectional view taken along line A-A of FIG. 2.
FIG. 4 is a perspective view of an embodiment of an article of
footwear of the present invention.
FIG. 5 is an alternative depiction of the manufacturing process
used to form a bladder of an article of footwear of the present
invention.
FIG. 6 is an alternative depiction of the manufacturing process
used to form a bladder of an article of footwear of the present
invention.
The present invention will be described with reference to the
accompanying drawings. The drawing in which an element first
appears is typically indicated by the leftmost digit(s) in the
corresponding reference number.
DETAILED DESCRIPTION OF THE INVENTION
It is desirable for inflatable bladders for athletic shoes to be
light weight, flexible and simple to manufacture. FIG. 1
illustrates one method for manufacturing an inflatable bladder 100
for use in athletic shoes. Bladder 100 may be formed from a first
sheet 102 and a second sheet 104 of a flexible, fluid-impervious
thermoplastic film. First sheet 102 has an exterior surface 102a
and an interior surface 102b, and second sheet 104 has an exterior
surface 104a and an interior surface 104b. Bladder 100 is formed
where first sheet 102 and second sheet 104 are sealed together. For
example, in FIG. 1, first sheet 102 and second sheet 104 are sealed
along an air-tight peripheral weld line 106. Narrow channels 108,
109, 110, 112 and 114 are formed within bladder 100, where interior
weld lines 116 further seal first sheet 102 to second sheet 104. In
order to avoid tight flow tolerances within narrow channels 108,
109, 110, 112 and 114 or anywhere else in bladder 100, bladder 100
may include an air passage device between the interior surface 102b
of first sheet 102 and interior surface 104b of second sheet 104.
The air passage device may be an embossed or texturized surface of
at least one of interior surface 102b or interior surface 104b or a
mechanical device inserted into the bladder, both of which are
described in further detail below. The air passage device provides
space between first sheet 102 and second sheet 104 within a narrow
channel, alleviates constriction of air flow through these narrow
channels and avoids noise caused by air flow restriction.
Sheets 102 and 104 may be similar or different materials provided
that they are each made from a fluid-impervious thermoplastic film
and that they may be bonded together to form an air-tight seal.
Sheets 102 and 104 include at least a layer of a thin thermoplastic
film. Thermoplastic films can be formed from a variety of
thermoplastic resins or other elastomeric materials, including, but
not limited to, polyurethanes (TPU),
ethylenevinylacetate/polyethylene copolymer; polyester elastomer
(Hytrel); ethylenevinylacetate/polypropylene copolymer;
polyethylene; polypropylene; neoprene; natural rubber;
dacron/polyester; polyvinylchloride; thermoplastic rubbers; nitrile
rubber; butyl rubber; sulfide rubber; polyvinyl acetate; methyl
rubber; buna N.; buna S.; polystyrene; ethylene propylene;
polybutadiene; polypropylene; silicone rubber, chlorsulfonated
polyethylene, nylon and other thermoplastic or elastomeric
materials. One particular example is a polyester urethane film
having a 85A shore hardness and a melting temperature of
150.degree. C., available from Hyo-Sung Corp. (Korea). One skilled
in the art can appreciate that any number of thermoplastic or
elastomeric materials are suitable for use in the present
invention, provided such material is fluid-impervious and capable
of forming an air-tight seal with a similar or different
thermoplastic or elastomeric materials.
As discussed above, sheets 102 and 104 are sealed together along a
peripheral weld line 106. Several methods have been developed to
form an air tight seal between sheets of thermoplastic films. Some
non-limiting examples of sealing techniques include ultrasonic
welding, radio frequency (RF) welding, thermal welding and airtight
adhesive bonding. One skilled in the art can appreciate that the
particular choice of sealing techniques is dependent upon the type
of material used for first sheet 102 and second sheet 104.
The thermoplastic film may be used alone to form bladder 100 or the
thermoplastic film may be formed as a laminate of the thermoplastic
film and a substrate. In this embodiment, the substrate generally
forms the exterior surface 102a of first sheet 102, the exterior
surface 104a of second sheet 104 or both, such that the interior
surfaces 102b and 104b, which contact each other, are thermoplastic
films.
Substrates may be any of a variety of textiles, for example any
synthetic or natural fibers or fabrics. One non-limiting example of
a fabric used as a laminate in bladders for athletic shoes is a
non-woven high density 70% nylon and 30% polyester blend, available
from Dae Woo International Corp. (Pusan, Korea). Several methods
have been developed to form laminates between thermoplastic films
and substrates. One such method includes direct cast extrusion of a
thermoplastic resin onto a substrate to form a thin film thereon.
Provided that the substrate is at least partially porous, the
thermoplastic film will permeate a portion of the substrate and
bond thereto. Other laminate forming methods known to those skilled
in the art would also be suitable for forming a laminate of the
present invention. For example, a laminate may be formed from a
thermoplastic film and a substrate by adhering the thermoplastic
film to the substrate via heat and pressure, via an adhesive
bonding material or via ultrasonic bonding. In another embodiment,
first sheet 102 and/or second sheet 104 may be made from a
multiple-layer laminate including one or more thermoplastic film
layers and one or more substrate layers, provided that the laminate
is fluid-impervious and an air tight seal may be formed between
interior surface 102b and interior surface 104b.
Unlike the matted polyurethane conventionally used to form
inflatable bladders for footwear, FIGS. 2 and 3 show an example of
a piece of a thermoplastic film 220, which may be used to form a
bladder of the present invention, such as bladder 100 of FIG. 1.
FIG. 3 is a cross section taken along line A-A of FIG. 2.
Thermoplastic film 220 has a first surface 222 and a second surface
324. First surface 222 is an embossed or textured surface having
raised areas 236 on a lower-profile background area 238. An
embossed or textured surface is preferably used as interior surface
102b, as interior surface 104b, or both of the bladder shown in
FIG. 1. Having at least one embossed interior surface provides less
contact between the interior surface 102b and interior surface
104b, to avoid adhesion or sticking between first sheet 102 and
second sheet 104. Additionally, the embossed interior surface
reduces or eliminates noise in fluid channels, such as channels
108, 109, 110, 112 and 114 of bladder 100, by providing additional
flow clearances to improve air movement between first sheet 102 and
second sheet 104. In another embodiment, first surface 222 may also
be used to form exterior surface 102a, exterior surface 104a or
both, for example when a particular texture is desired on the
exterior of a shoe upper. In yet another embodiment, both first
surface 222 and second surface 324 may be embossed similar to first
surface 222 in FIGS. 2 and 3.
An advantage provided by the embossed surface comes from the
particular depth between the raised areas 236. The raised areas 236
in the embodiment of FIGS. 2 and 3 are generally diamond-shaped and
may protrude about 0.01 mm to about 0.10 mm from the lower-profile
background area 238, preferably about 0.05 mm to about 0.90 mm. The
overall thickness of the thermoplastic film 220 is about 0.20 mm to
about 0.40 mm. However, a most preferred thermoplastic film may
include raised areas 236 that protrude about 0.8 mm from
lower-profile background area 238, with an overall thickness of the
thermoplastic film being about 0.30 mm to about 0.32 mm. One
skilled in the art can appreciate that embossed surfaces may have a
variety of textures or pattems and may have raised areas that have
a variety of dimensions and protrude any distance from a
lower-profile background area, provided that the embossed surface
enhances air movement through narrow channels. Further, an embossed
surface may have no consistency in the dimensions of various
adjacent raised areas.
The embossed first surface 222 may be added to a thermoplastic film
in several ways. For example, a thermoplastic resin which has been
extruded into a thin film may be subsequently embossed in a
continuous process via an emboss roller at the casting location,
whether or not cast onto a substrate as discussed in detail above.
An emboss roller imprints the embossed pattern into the surface of
the thermoplastic film. Alternatively, a thermoplastic film may be
subsequently heated and embossed on a similar emboss roller. A
thermoplastic film may be embossed before or after being bonded to
a substrate, in the manner discussed above. Downstream from the
emboss roller, a thickness sensor may be employed to gauge the
consistency of the embossed dimensions. Alternatively, commercially
available embossed material may be used in forming bladder 100 of
FIG. 1.
In the embodiment in FIG. 1, an inflation device 118, including a
one-way valve 118a, and a deflation device 119 have been
incorporated into bladder 100. However, in alternative embodiments,
an inflation device and a deflation device may be attached after
forming bladder 100. For example, an inflation device may be a
separate entity which is later coupled to bladder 100 via tubing or
other fluid conduits. In yet another embodiment, an inflation
device may not be an "on-board" inflation device. Instead, the
inflation device may be temporarily coupled to bladder 100 via a
valve only when inflation is desired by the user. Some examples of
inflation and deflation devices, including self-actuating inflation
devices, are more fully described in U.S. patent application Ser.
No. 10/887,927, which is incorporated herein in its entirety by
reference. One skilled in the art can appreciate that a variety of
inflation and/or deflation devices may be provided in a bladder of
the present invention.
Once formed, bladder 100 is cut away from the remaining portions of
first sheet 102 and second sheet 104 along an exterior edge 106a of
the peripheral weld line 106 and incorporated into an article of
footwear. Bladder 100 may be bonded, such as by the use of
adhesives or other bonding techniques, or sewed to other shoe
materials, preferably along the peripheral weld line 106.
FIG. 4 illustrates a shoe 440 including a bladder 400 formed by the
method illustrated in FIG. 1. Although FIG. 4 illustrates a right
shoe, a left shoe would be a mirror image of shoe 440. Shoe 440
includes an upper 442 and a sole 444 attached to upper 442. In the
embodiment of FIG. 4, bladder 400 is part of upper 442 and extends
under the foot of the wearer and into sole 444. In alternative
embodiments, a bladder may be positioned within a shoe in only an
upper or a sole. Further, bladder 400 may be used alone to form a
portion of the upper, or may be combined with other cushioning
materials, or any other conventional upper materials, to add
comfort to the wearer. Similarly, bladder 400 placed in the sole of
a shoe may be supported by conventional sole material, for example
EVA foam or a lightweight durable EVA foam composite for supporting
and cushioning the wearer's foot from forces exerted during normal
exercise or athletic activity.
Utilizing an embossed material is only one air passage device that
may be used to alleviate air flow restrictions within narrow
channels. In other embodiments, such as those shown in FIGS. 5 and
6, mechanical devices may be inserted into the narrow channels to
avoid constriction caused by the thermoplastic films. For example,
in FIG. 5, a small piece of reticulated or open celled foam 550 may
be placed in a localized area within a bladder 500 where air flow
restriction may occur. The foam 550 holds the first sheet 502
spaced apart from second sheet 504 in narrow channels, such as
within narrow channel 509. FIG. 6 illustrates another type of
mechanical device placed within a narrow channel 609 of a bladder
600. In this embodiment, a stent 660 or a piece of tubing, may be
inserted into a narrow channel 609 of an inflatable bladder 600.
Stent 660 will also hold apart sheet 602 from sheet 604 to allow
air to flow freely in narrow channel 609 and alleviate air flow
constriction in this area. One skilled in the art can appreciate
that any number of mechanical devices, such as a set of ribs or a
piece of any textile substrate, may be positioned within a narrow
channel to maintain the air passage provided between a first and
second sheet of thermoplastic film. In yet another embodiment, a
substrate, such as the substrates described above may be laminated,
as discussed above, to a particular location on an interior surface
of one of a first sheet or a second sheet to avoid having the first
sheet adhere to the second sheet and to maintain the air passage
between the first and the second sheets, for example in a narrow
channel of a bladder. A bladder including a mechanical device, such
as those described above, may also be used in a shoe, such as that
described above with respect to FIG. 4.
The foregoing description of the specific embodiments will so fully
reveal the general nature of the invention that others can, by
applying knowledge within the skill of the art (including the
contents of the references cited herein), readily modify and/or
adapt for various applications such specific embodiments, without
undue experimentation, without departing from the general concept
of the present invention. Therefore, such adaptations and
modifications are intended to be within the meaning and range of
equivalents of the disclosed embodiments, based on the teaching and
guidance presented herein. It is to be understood that the
phraseology or terminology herein is for the purpose of description
and not of limitation, such that the terminology or phraseology of
the present specification is to be interpreted by the skilled
artisan in light of the teachings and guidance presented herein, in
combination with the knowledge of one of ordinary skill in the
art.
* * * * *
References